Some people are electrically sensitive, that is they are aware of the presence of electromagnetic fields (EMFs), but are not adversely affected by them. Other people may or may not be aware of the presence of EMFs, but can become seriously ill in their presence. These people we refer to as electrically hypersensitive (EHS). People who have developed EHS have a physiological disorder, characterized by neurological and idiopathic reactions, that noticeably appear or intensify near sources of EMFs such as electrical appliances, especially VDUs (computer monitors), power lines, fluorescent lights, mobile phones, cordless phones, wireless computers (wLANs), mobile phone base stations, etc.

Being EHS means experiencing recurring feelings of stress or illness when near an EMF source. Any noticeable, recurring ill health that is triggered by an electromagnetic field, and that diminishes or disappears away from the EMF source, constitutes a case of electrical hypersensitivity. While symptoms may diminish quickly after the exposure is reduced, it can take several days, weeks or occasionally months if the person has become severely sensitised, for the effects to disappear.